The invention relates to a motion nut for a lifting device, especially a mechanical car jack, comprising a basic body, which is provided with an internal thread for seating a threaded spindle.
The EP-B 0320613 relates to a car jack with a platform leg, at which a supporting arm, which can be swiveled about a horizontal axis, is hinged and which is engaged by a threaded spindle, which is mounted at the platform leg in an articulated fashion with a plastic spindle nut, which engages, with stud axles, bearing recesses of the platform leg form as a shaped sheet-metal part. A metal bracket is connected positively with the plastic spindle nut and has, at its ends, the stud axles of the spindle nut in the region of the bearing recesses of the supporting segments covering the platform leg. Disadvantageously, it may be noted here that the region, accommodating the threaded spindle, must be reinforced by a further component (metal bracket), structural changes also having to be made to the plastic spindle nut, so that the two components can be positioned accurately relative to one another.
A similar construction is described in the EP-A 0340551. The spindle nut consists of a plastic body, which interacts with a metallic reinforcing element. The reinforcing element comprises a sleeve-like projection of the plastic body and is constructed as a sheet-metal ring. The criteria, which apply here, are identical with those already described.
A spindle nut connection can be inferred from U.S. Pat. No. 2,664,023. The region of the spindle nut is formed here by a two-part sleeve, the two parts of which are connected together by means of a spring element and over which a one-part bushing, having an internal contour corresponding to the sleeve accommodation region, is pushed later on. Aside from the tolerances, which must be maintained here between the threaded spindle and the divided, threaded nut, this type of structural configuration of a motion nut must be regarded as cumbersome and component-intensive.